I have a blog running on blogger using my own domain (lets say www.example.com).
The standard blogger Atom feed is available at www.example.com/feeds/posts/default

Now I want to migrate my blog to a self hosted custom application without loosing atom feed subscribers. My new blog will also be available at www.example.com. The new atom feed is available at www.example.com/feeds/atom. I have full control over urls and the generation of the new atom feed.

Atom feed entries that have been migrated from the old blog will use the same <id> that has been used in the blogger atom feed. (I am not sure if this is necessary but according to this question, feed entry ids should not change)

If you are in "full control over urls" then you could generate your atom feed at the same URL and not bother with the redirection? (Do all news readers follow redirection?) Alternatively, you could internally rewrite the request from /feeds/posts/default to /feeds/atom - again, no need for a redirection?
– MrWhiteAug 15 '15 at 16:40

You are right, I should probably rewrite the request internally to the new url, thanks.
– KolfAug 17 '15 at 8:28